Field
The present disclosure relates to a fuel-cell unit cell.
Related Art
Generally, a fuel cell has a fuel cell stack in which a plurality of unit cells are stacked. Each unit cell has a membrane electrode and gas diffusion layer assembly with a power generation region therein, and two separators for sandwiching the membrane electrode and gas diffusion layer assembly therebetween. The membrane electrode and gas diffusion layer assembly is formed such that one electrolyte membrane is sandwiched between two electrode catalyst layers, which are further sandwiched between two gas diffusion layers. The power generation region is a region coincident with a region over which the two electrode catalyst layers overlap with each other. On one surface of each separator, a plurality of reactant gas flow paths are formed for supplying reactant gas to the membrane electrode and gas diffusion layer assembly. In more detail, a plurality of fuel gas flow paths (anode gas flow paths) are formed on one surface of the anode-side separator out of the two separators, and a plurality of oxidizing gas flow paths (cathode gas flow paths) are formed on one surface of the cathode-side separator. The fuel cell stack has, in general, a stack structure in which an anode-side separator and a cathode-side separator of neighboring unit cells are in contact with each other.
WO 2013/105956A describes a fuel cell in which constricting portions are provided in both the anode gas flow paths and the cathode gas flow paths in order to efficiently supply anode gas and cathode gas to the membrane electrode and gas diffusion layer assembly. The constricting portions are formed by reducing the height of the gas flow paths. Whereas neighboring separators of two unit cells are in contact with each other at outer walls of protruded portions of the gas flow paths, the separators structurally do not contact each other at the constricting portions that are smaller in height in the gas flow paths.
As to the cathode gas flow paths and the anode gas flow paths, their proper two-dimensional shapes may differ depending on their desirable characteristics. For example, for the cathode gas flow paths, their preferable flow path shapes are those allowing easier discharge of liquid water generated by fuel cell reactions. On the other hand, for the anode gas flow paths, such flow path shapes are preferable as to enhance the utilization efficiency of the anode gas (e.g., hydrogen). Also, their preferable flow path shapes may differ from each other depending on the placement of gas manifold holes as well. Thus, when the cathode gas flow paths and the anode gas flow paths are different in two-dimensional shape from each other, there is a possibility that contact portions between the cathode-side separator and the anode-side separator of neighboring two fuel-cell unit cells are reduced, as compared with cases in which the gas flow paths are of an identical two-dimensional shape as in WO 2013/105956A. For this reason, there has been a problem that depending on the positions of the constricting portions, contact portions over which the cathode-side separator and the anode-side separator of neighboring two fuel-cell unit cells are in contact with each other may be reduced, with the result that compressive force may be concentrated excessively to the other portions.